1)I dont use Yahoo mail so cant comment on that
2)I don't know what you've done to get it to do that, But I have 10+ Macs which render perfectly.
3)After updating your firefox it will re-launch its self twice to update your profile (don't be impatient give it a sec)
4)What the?, If your talking about the theme add on you like.

My Review: Faster load times over 0.8, Render Time slightly improved, theme and extension managment has vastly improved over 0.8 .
I Don't like the new default theme Im using Noia Extreme, but Qute (The old Default) is still good. And the Google bar needs to be resizable (Like Safari)